Thermodynamic regenerator

ABSTRACT

Various embodiments are directed to a regenerator for use with a regenerative engine. The regenerator may comprise a plurality of regenerator disks. Each of the plurality of regenerator disks may comprises a plurality of concentric ribs defining a plurality of concentric gaps therebetween. Further, the plurality regenerator disks may be arranged within the regenerator longitudinally, such that the plurality of concentric gaps defined by adjacent regenerator disks are substantially aligned.

BACKGROUND

Regenerative engines are used in many contexts to translate energy between heat and motion. To accomplish this transformation, regenerative engines typically utilize a thermodynamic cycle. Mechanical energy (often involving the compression and expansion of a fluid) is used to shift heat energy, creating a hot source and a cold source. Regenerative engines in this configuration are often utilized as mechanical coolers. Mechanical coolers are used for many purposes including, for example, to cool certain sensor elements, to cool materials during semiconductor fabrication, and to cool superconducting materials such as in Magnetic Resonance Imaging (MRI) systems. Cryocoolers are a class of mechanical coolers that can achieve cold temperatures in the cryogenic range (e.g., <˜123 K). Regenerative engines are also operated in a configuration opposite that described above to translate heat energy to motion. A concentration of heat energy causes compression and expansion of the fluid, which may be used to for various mechanical purposes. Different types of regenerative engines may comprise various valves, thermal compressors, mechanical compressors, displacers, etc., to bring about expansion and compression of the working fluid.

One type of regenerative engine is a pulse tube engine. A pulse tube engine includes a stationary regenerator connected to a pulse tube. A reservoir or buffer volume may be connected to the opposite end of the pulse tube via a phase control device such as a sharp-edged orifice or an inertance tube. The reservoir, pulse tube, and regenerator may be filled with a working fluid (e.g., a gas such as helium). A compressor (e.g., a piston) may compress and warm the working fluid. The compressed working fluid is forced through the regenerator, where part of the heat from the compression is removed at ambient temperature. As the working fluid is passed through the regenerator, it exchanges heat with the regenerator matrix, causing the working fluid to cool down and the regenerator to heat up. The working fluid is then expanded through the pulse tube and the phase control device into the reservoir. This expansion provides further cooling that takes place at a cold temperature. Additional heat is rejected at the end of the pulse tube farthest from the regenerator. Cooling occurs at a cold end of the pulse tube nearest the regenerator. A hot end of the pulse tube farthest from the regenerator collects heat. In an alternate configuration, the pulse tube engine operates in reverse with heat provided at the hot end of the pulse tube bringing about expansion of the working fluid and motion of the piston. Other types of regenerative engines utilize various other means for forcing the working fluid through the regenerator. For example, a Stirling engine utilizes a compressor/piston on both ends of the regenerator. Other types of regenerative engines include Gifford-McMahon engines, Solvay engines, Vulleumier engines, etc.

The performance of regenerative engines depends largely upon the performance of the regenerator. An ideal regenerator will achieve a maximum heat transfer to and/or from the working fluid and a minimum pressure drop in the working fluid across the regenerator. One existing regenerator design involves packing screen material made of a high heat capacity material into a cylindrical package. Working fluid flowing through the regenerator deposits heat to and/or absorbs heat from the screen materials. Screen material regenerators, however, suffer from several problems. With many screen materials, small bits of screen can come apart, clogging openings in the screen and an increasing pressure drops. Also, the pressure drop across a screen regenerator is highly dependent on the manner in which the screen material is packed. If screen material is packed too tightly, unacceptably high pressure drops may occur. Another existing regenerator type is often referred to as a “jelly roll” regenerator. A jelly roll regenerator is formed from a flat piece of high heat capacity material. Spacers are placed on the material and it is rolled upon itself. The spacers create interior channels. In use, working fluid is made to flow through the channels, where the fluid may deposit heat to and receive heat from the regenerator material. The effectiveness of jelly roll regenerators, however, is highly dependant on the manufacturing and mechanical integrity of the interior channels. If the channels are not all of the same width, then working fluid will primarily flow through the channel offering the least resistance, compromising the effectiveness of the regenerator.

SUMMARY

Various embodiments are directed to a regenerator for use with a regenerative engine. The regenerator may comprise a plurality of regenerator disks. Each of the plurality of regenerator disks may comprises a plurality of ribs defining gaps therebetween. In some embodiments, the gaps may be concentric. Further, the plurality regenerator disks may be arranged within the regenerator longitudinally, such that the plurality of concentric gaps defined by adjacent regenerator disks are substantially aligned.

FIGURES

Various embodiments of the present invention are described here by way of example in conjunction with the following figures, wherein:

FIG. 1 illustrates one embodiment of an example concentric gap disk regenerator for use with a regenerative engine.

FIG. 2 illustrates a cross-sectional view of one embodiment of the regenerator of FIG. 1 comprising an outer cylinder for receiving the disks.

FIG. 3 illustrates a cross-sectional view of one embodiment of the regenerator of FIG. 1 comprising a shrink tube for receiving the disks.

FIG. 4 illustrates one embodiment of a disk of the regenerator of FIG. 1 showing the concentric gaps.

FIG. 5 illustrates one embodiment of a disk of the regenerator of FIG. 1 having concentric ribs at different distances from the common center offset from one another.

FIG. 6 illustrates a side cross-sectional view of one embodiment of a disk of the regenerator of FIG. 1 having alignment groove and ridge.

FIG. 7 illustrates a top view of one embodiment of the disk of FIG. 6 showing the groove illustrated in FIG. 6.

FIG. 8 illustrates a top view of another embodiment of the disk of FIG. 6 where the groove is not continuous about the common center.

FIG. 9 illustrates a cross-sectional view of one embodiment of the disk of FIG. 8 showing non-continuous recesses and corresponding non-continuous ridges.

FIG. 10 illustrates a cross-sectional view of one embodiment of a disk of the regenerator of FIG. 1 having a groove and an insulating ridge.

FIG. 11 illustrates one embodiment of a pulse tube regenerative engine utilizing the regenerator of FIG. 1.

FIG. 12 illustrates another embodiment of a pulse tube regenerative engine utilizing the regenerator of FIG. 1.

FIG. 13 illustrates one embodiment of a chart showing a modeled performance of the regenerator of FIG. 1 in a regenerative pulse tube cooler.

FIG. 14 illustrates one embodiment of the disk of the regenerator of FIG. 1 having non-concentric linear gaps.

FIG. 15 illustrates one embodiment of the disk of the regenerator of FIG. 1 having gaps exhibiting a non-concentric gap pattern.

DESCRIPTION

Various embodiments may be directed to regenerators for use with regenerative engines. The regenerators may comprise a plurality of disks. Each disk may define a plurality of concentric gaps. The disks may be arranged longitudinally within the regenerator such that the gaps are substantially aligned. In this way, the gaps may form longitudinal channels through the regenerator. When the regenerator is used with a regenerative engine, working fluid may be passed through the longitudinal channels to transfer heat energy to and from the disks. The width of each longitudinal channel may be related to the width of the respective gaps in each disk. According to various embodiments, concentric gap disk regenerators may enjoy several advantages. For example, manufacturing techniques for repeatedly manufacturing concentric gap disks to within acceptable tolerances may be more practical and less expensive than those used with existing regenerators. Also, variations in gap width from disk to disk may be roughly cancelled out over the longitudinal distance of the regenerator. In this way, the fluid resistance of the various longitudinal channels may be relatively equal, leading to greater regenerator performance and, in some cases, less stringent tolerances.

FIG. 1 illustrates one embodiment of an example concentric gap disk regenerator 100 for use with a regenerative engine. The regenerator 100 is illustrated connected to two working fluid flow tubes 102, 104. Fluid may enter and exit the regenerator 100 via the fluid flow tubes 102, 104. As illustrated, the regenerator 100 may be formed from a plurality of disks 110. The disks 110 may be arranged along a longitudinal axis 106 of the regenerator 100 as shown. The disks 110 may be held in place according to any suitable method or mechanism. In various embodiments, the disks 100 may be mechanically fastened to one another. The fastening may be accomplished using any suitable method or combination of methods. For example, an adhesive may be used to secure the disks 110 to one another. Alternatively, or additionally, a fastener device (not shown) such as a screw, bolt, or rod may be utilized to fasten the disks 110 to one another. In some embodiments, the disks 110 may be sintered to one another.

According to various embodiments, the disks 110 may be held in place within the regenerator 100 via an exterior frame or other material. For example, FIG. 2 illustrates a cross-sectional view of one embodiment of the regenerator 100 comprising an outer cylinder 202 for receiving the disks 110. The outer cylinder 202 may be made from any suitable material and, in various embodiments. According to various embodiments, the outer cylinder 202 may be made from a material having a relatively poor thermal conductivity such as, for example, a plastic. The cylinder 202 may have a cap 204 positioned at each end of the regenerator to secure the disks 110. The caps 204 may partially cover the ends of the cylinder 202 or, according to various embodiments, may fully cover the ends of the cylinder 202. In various embodiments, the caps 204 may interface with the working fluid flow tubes 102, 104.

In some embodiments, a shrink tube may be utilized to secure the disks 110 within the regenerator 100. For example, FIG. 3 illustrates a cross-sectional view of one embodiment of the regenerator 100 comprising a shrink tube 302 for receiving the disks. The shrink tube 302 may be made from any suitable material that expands when heated and contracts when cooled (e.g., a plastic). At the desired operating temperature, the shrink tube 302 may have a diameter slightly less than the diameter of the respective disks 110. During manufacturing, the shrink tube 302 may be heated, for example, by an industrial oven, an infrared lamp, etc. This may cause the shrink tube 302 to expand and its diameter to increase to a size slightly larger than the diameter of the disks 110. While the shrink tube 302 is heated and its diameter is increased, the disks 110 may be placed within the tube 302, which may then be allowed to cool. When the shrink tube 302 cools, it may contract, holding the disks in place, as shown.

FIG. 4 illustrates one embodiment of a disk 110 of the regenerator 100 showing the concentric gaps 402. The disk 110 may be made from any suitable material. For example, in various embodiments, the disk 110 may be made from a material with a high heat capacity, such as stainless steel, phosphor bronze, lead, and/or a rare earth metal such as, scandium, yttrium, lanthanum, cerium, etc., and alloys thereof. The diameter of the disk 110 may be any suitable distance. For example, according to various embodiments, the diameter of the disk 110 may be between about ¼ of one inch and one foot.

As illustrated, the gaps 402 may be defined by a plurality of ribs 404 formed in the face of the disk 110. The gaps 402 and the ribs 404 may be concentric (e.g., around a common center 406). The common center 406 may be at the center of the disk 110. It will be appreciated that although the disk 110 shown in FIG. 4 is a circle, disks 110 according to various embodiments may have any suitable shape including, for example, polygonal, ovaloid, etc. According to various embodiments, the ribs 404 (and therefore the gaps 402) may extend partially (e.g., less than 360°) around the common center. For example, each of the ribs 404 shown in FIG. 4 may extend about 120° about the common center 406. Accordingly, there may be three separate ribs 404 at any given distance from the common center 406. It will be appreciated that the ribs 404 and, therefore, the gaps 402 may have any suitable angular extension about the center 406. For example, in some embodiments, individual ribs 404 and/or gaps 402 may extend 90°, 180°, 60°, etc. Ribs 404 at the same distance from the center 406 may be separated by tabs 408. The tabs 408 may serve to join the ribs 404 to one another and to the remainder of the disk 110.

As illustrated in FIG. 4, the angular positions of all of the ribs 404 at different distances from the common center 406 are aligned. In various embodiments, however, the angular positions of the ribs 404 at different distances from the center 406 may be offset from one another. For example, FIG. 5 illustrates one embodiment of the disk 110 of the regenerator 100 having concentric ribs 404 at different distances from the common center 406 offset from one another. As illustrated, offsetting the angular positions of the ribs 404 about the center 406 may distribute the tabs 408 about the center 406. In some embodiments, this may increase the mechanical strength of the disk 110 by better supporting the gaps 402.

FIG. 6 illustrates a side cross-sectional view of one embodiment of the disk 110 having an alignment groove 602 and ridge 604. FIG. 7 illustrates a top view of one embodiment of the disk 110 showing the groove 602 illustrated in FIG. 6. The ribs 404 and gaps 402 described herein are not specifically illustrated in FIG. 7, but may be included in the shaded portion 605, for example, in the manner shown in FIGS. 4 and 5. The alignment groove 602 may be present on a first surface 601 of the disk 110. A corresponding ridge 604 may be present on an opposite surface 603 of the disk 110. When successive disks 110 are stacked to form the regenerator 100, the groove 602 of the disk 110 may receive the corresponding ridge of the disk immediately next to it. Likewise, the ridge 604 of the disk 110 may be received into the corresponding groove of the disk on the opposite side of the disk 110. In this way, the alignment of the disks of the regenerator 110 may be maintained. As illustrated in FIG. 7, the groove 602 extends continuously for 360° around a center of the disk 110. In other embodiments, however, the groove 602 may be discontinuous. In some of these embodiments, the ridge 604 may have corresponding discontinuities such that the groove 602 and ridge 604 of adjacent disks 110 interconnect, as described herein. In this way, the groove 602 and ridge 604 may maintain rotational as well as positional alignment of the disks 110.

FIG. 8 illustrates a top view of another embodiment of the disk 110 where the groove 602 is not continuous. For example, the groove, as illustrated in FIG. 8, may comprise a series of recesses 802. FIG. 9 illustrates a cross-sectional view of one embodiment of the disk 110 showing the non-continuous recesses 802 and corresponding non-continuous pegs 804. The recesses 802 may be on a first surface 801 of the disk 110. The recesses 802 may be spaced around a perimeter of the disk 110 as illustrated, or may be formed on the disk in any suitable pattern. Referring to FIG. 9, the disk 110 may also have a plurality of alignment pegs 804. The position of the alignment pegs 804 may correspond to the position of the recesses 802 such that when the disks 110 are formed into the regenerator, the recesses 802 of most disks 110 receive the pegs 804 of the adjacent disk. In this way, the spatial and rotational alignment of the disks 110 may be maintained.

According to various embodiments, it may be desirable for the thermal conductivity between adjacent disks 110 to be minimized. For example, materials that have a high heat capacity, such as stainless steel and other metals, may also have a high thermal conductivity. Excessive thermal conductivity within the regenerator 100 may lead to heat loss, reducing the effectiveness of the regenerator 100. Thermal conductivity within the regenerator 100 may be reduced in any of a number of methods. For example, alternating disks 110 in the regenerator may be made from and/or coated (e.g., completely or partially) with a thermally insulating material (e.g., plastic, rubber, etc.).

FIG. 10 illustrates a cross-sectional view of one embodiment of the disk 110 having a groove 1002 and an insulating ridge 1004. The ridge 1004 may be made from a thermally insulating material, such as a rubber, a plastic, etc. When the disk 110 is brought into contact with adjacent disks 110, the ridge 1004 may limit the thermal contact between disks, thus reducing the overall thermal conductivity within the regenerator 100. According to various embodiments, the ridge 1004 may extend from the surface 1003 of the disk slightly farther than the groove 1002 extends into the surface 1001 of the disk 110. This may cause a slight gap between adjacent disks, further reducing the thermal conductivity within the regenerator 100. It will be appreciated that similar embodiments may utilize the recesses 802 and pegs 804 shown in FIGS. 8-9. For example, the pegs 804 may comprise a thermally insulating material and, in some embodiments, may extend beyond the surface 803 of the disk 110 farther than the recesses 802 extend below the surface 801 of the disk 110.

It will be appreciated that the regenerator 100 and the disks 110 may be of any suitable dimensions. For example, length of the regenerator 110 along the longitudinal axis 106 may be determined based on the thickness of each disk 110 and the number of disks present. In various embodiments, the length of the regenerator 110 may exceed its width (e.g., the width of the regenerator may be the same as the diameter of the disks 110. Also, in various embodiments, the thickness of the disks may be about 130 μm. Similarly, the width of the ribs 404 and gaps 402 may vary in various embodiments and may be selected to optimize performance. For example, in various embodiments, the width of the gaps 402 may vary between about 20 μm and about 30 μm. Also, in various embodiments, the width of the ribs 404 may vary from between about 30 μm and about 130 μm.

The regenerator disks 110 described herein may be manufactured according to any suitable manufacturing method. For example, the disks 110 may be manufactured utilizing a machining technique. Disk blanks may be provided to a machining device, which may cut out the gaps 402 and/or to cut-down around features such as ridges 604, 1004, pegs 804, etc. to form a finished product. Any suitable machining technique may be used. For example, in some embodiments, electric discharge machining (EDM) may be utilized. EDM methods utilize electrical discharges to ablate unwanted material. Also, in some embodiments, the disks 110 may be machined according to a laser direct write method. An example of such a method is disclosed in U.S. Pat. No. 6,783,920 to Livingston, et al., entitled “Photosensitive Glass Variable Exposure Patterning Method,” which is incorporated herein by reference in its entirety. Other example machining methods that may be used include, diamond tool machining, water jet machining, etc.

Also, in various embodiments, the disks 110 may be formed from additive manufacturing methods. For example, the disks 110 may be formed utilizing a powder, which may be formed into the desired shape and then baked. In some embodiments, a laser sintering technique may be used. For example, a laser may be used to heat and/or bind a powder or other loosely bound material into the desired shape. Also, in various embodiments, the disks 110 may be formed by embedding a desired disk material into a polymeric binder. The binder may ultimately be removed (e.g., by melting, etc.), leaving the disk material. Still other example methods that could be used to manufacture the disk 110 may include, using a punch, chemical etch lithography, etc.

FIG. 11 illustrates one embodiment of a pulse tube regenerative engine 1100 utilizing the regenerator 100. The engine 1100, as shown, is configured as a cooler. It 1100 comprises various components in fluid communication with one another and filled with a working fluid (e.g., helium gas). For example, the engine 1100 may comprise a compressor 1102 for providing pressure/volume (PV) work. The compressor 1102 may be of any suitable compressor type and, in various embodiments, may be a linear compressor or rotary compressor. In various embodiments, the compressor 1102 may comprise a piston 1118 and a cylinder 1120. In addition, the engine 1100 may comprise the regenerator 100, a pulse tube 1106 and a reservoir 1108. A first heat exchanger 1110 may be positioned between the compressor 1102 and the regenerator 100. A cold end heat exchanger 1112 may be positioned at a cold end 1199 of the pulse tube 1106 near the regenerator 100. A hot end heat exchanger 1114 may be positioned at a hot end 1198 of the pulse tube 1106 near the reservoir 1108. The reservoir 1108 and the pulse tube 1106 may be connected by a phase control device 1116 that may comprise one or more sub-devices having an inertance and/or a resistance to the flow of working fluid. The phase control device 1116 may be embodied as one or more separate components, as a portion of the pulse tube 1106, as a portion of the reservoir 1108, or as any combination thereof.

The compressor 1102, may drive the thermodynamic cycle of the engine 1100 at various frequencies. For example, in various embodiments, one thermodynamic cycle of the engine 1100 may correspond to one complete cycle of the piston 1102 or other mechanism of the compressor 1102. According to the thermodynamic cycle of the engine 1100, the compressor 1102 may provide work to compress a portion of the working fluid, adding heat and causing the temperature of the working fluid to rise at heat exchanger 1110. The heat of compression may be removed to the ambient. As the compressor 1102 further compresses, warm working fluid is passed through the regenerator 100, where the working fluid is cooled and the energy stored in the regenerator material. Working fluid already present in the pulse tube 1106 may be at a relatively lower pressure than that entering the pulse tube via 1106 via the regenerator 100. Accordingly, the working fluid entering the pulse tube 1106 via the regenerator 100 may expand in the pulse tube 1106, causing cooling at the exchanger 1112. Excess pressure in the pulse tube 1106 from the expansion may be relieved across the phase control device 1116 into the reservoir. As the cycle continues, the compressor 1102 begins to draw the working fluid from the cold end 1199 of the pulse tube 1106 back through the regenerator 100, where the stored heat is reintroduced. Resulting low pressure in the pulse tube 1106 may also cause working fluid from the reservoir 1108 to be drawn across the phase control device 1116 into the pulse tube 1106. This working fluid from the reservoir 1108 may be at a higher pressure than that already in the pulse tube 1106 and, therefore, may enter with heat energy and at a temperature that is relatively warmer than that of the other working fluid in the pulse tube 1106. A new cycle may begin as the compressor 1102 again reverses and begins to compress the working fluid. Examples of the operation of pulse tube engines are provided in the following commonly assigned U.S. Patent Applications: Publication No. 2009/0084114, entitled “Gas Phase-Shifting Inertance Gap Pulse Tube Cryocooler,” filed on Sep. 28, 2007; Publication No. 2009/0084115, entitled “Controlled and Variable Gas Phase Shifting Cryocooler,” filed on Sep. 28, 2007; Publication No. 2009/0084116, entitled “Gas Phase Shifting Multistage Displacer Cryocooler,” filed on Sep. 28, 2007; Ser. No. 12/611,764, entitled “Phase Shift Devices for Pulse Tube Coolers,” filed on Nov. 3, 2009; Ser. No. 12/611,774, entitled “Phase Shift Devices For Pulse Tube Coolers,” filed on Nov. 3, 2009; and Ser. No. 12/611,784, entitled “Multistage Pulse Tube Coolers,” filed on Nov. 3, 2009, all of which are incorporated herein by reference in their entirety.

FIG. 12 illustrates another embodiment of the pulse tube regenerative engine 1100 utilizing the regenerator 100. As illustrated in FIG. 12, the regenerator 100 may be directly coupled to the pulse tube 1106 without an intervening tube. In some embodiments, as shown, heat exchanger 1112 may be present between the regenerator 100 and the pulse tube 1106. According to various embodiments an outer cylinder 1202 of the pulse tube 1106 may also serve as an outer cylinder 1202 of the regenerator 100. For example, disks 110 may be installed into the outer cylinder 1202 in a manner similar to the way that the disks 110 are installed into the outer cylinder 202, as described herein. It will be appreciated that although FIGS. 11 and 12 show the regenerator 100 installed in a pulse tube engine 1100, the regenerators as described herein may be used in any other suitable type of regenerative engine or any other embodiment involving the storage and retrieval of thermal energy.

FIG. 13 illustrates one embodiment of a chart 1300 showing a modeled performance of the regenerator 100. The chart 1300 includes a plot 1302 showing regenerator rib thickness in μm versus cooling capacity in Watts. The cooling capacity may generally indicate the performance of the regenerator 100. The chart 1300 was generated utilizing the SAGE software package available from Gedeon Associates of Athens, Ohio. The cooling capacity of the regenerator 100 was modeled over various thicknesses of the ribs 404, with the thickness of the gap 402 held at 20 μm. As illustrated, the thickness of the ribs 404 was modeled over a range from 30 μm to 130 μm. The cooling capacity of a typical screen regenerator is indicated on the chart 1300 by point 1304. As shown, the performance of the regenerator 100 may exceed that of the typical screen regenerators over most of the range of modeled rib thicknesses.

According to various embodiments, the regenerator 100 may be constructed with disks exhibiting non-concentric patterns. For example, the disks may comprise ribs defining gaps that are linear, zig-zag or any other suitable pattern. In embodiments exhibiting non-concentric patterns, it may be desirable to achieve uniform alignment of the disks about the longitudinal axis of the regenerator 100 (e.g., uniform alignment of the gaps). This may reduce flow resistance (e.g., by creating channels that extend longitudinally through the regenerator 100). Disk alignment may be achieved in any suitable manner. For example, the disks may be constructed with non-continuous alignment grooves 602, as illustrated in FIG. 8. Any other suitable method and/or mechanism may be used.

FIG. 14 illustrates one embodiment of the disk 110 of the regenerator 100 having non-concentric linear gaps 1404. The non-concentric gaps 1404 may be defined by a plurality of ribs 1402 running therebetween. The gaps 1402 and ribs 1404 may be formed using any suitable manufacturing method or device including, for example, those described herein. FIG. 15 illustrates another embodiment of the disk 110 of the regenerator 100 having gaps 1504 exhibiting a non-concentric gap pattern. The pattern exhibited by gaps 1504 and corresponding ribs 1502 is a zig-zag pattern, with alternating portions of each rib 1502 meeting one another at angles of less than 180°. Any suitable pattern, however, may be used. The widths of the gaps 1402, 1502 and ribs 1404, 1504 may be of any suitable value. For example, in various embodiments, the width of the gaps 1404, 1504 may vary between about 20 μm and about 30 μm. Also, in various embodiments, the width of the ribs 1402, 1502 may vary from between about 30 μm and about 130 μm.

It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating other elements, for purposes of clarity. Those of ordinary skill in the art will recognize that these and other elements may be desirable. However, because such elements are well known in the art and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein.

In various embodiments disclosed herein, a single component may be replaced by multiple components and multiple components may be replaced by a single component to perform a given function or functions. Except where such substitution would not be operative, such substitution is within the intended scope of the embodiments.

Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated materials does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

While various embodiments have been described herein, it should be apparent that various modifications, alterations, and adaptations to those embodiments may occur to persons skilled in the art with attainment of at least some of the advantages. The disclosed embodiments are therefore intended to include all such modifications, alterations, and adaptations without departing from the scope of the embodiments as set forth herein. 

1. A regenerator for use with a regenerative engine, the regenerator comprising: a plurality of regenerator disks; wherein each of the plurality of regenerator disks comprises a plurality of ribs defining a plurality of gaps therebetween; and wherein the plurality regenerator disks are arranged within the regenerator longitudinally, such that the plurality of concentric gaps defined by adjacent regenerator disks are substantially aligned.
 2. The regenerator of claim 1, wherein the plurality of regenerator disks comprise at least one material selected from the group consisting of stainless steel, phosphor bronze, lead, and a rare-earth metal.
 3. The regenerator of claim 1, wherein a diameter of the plurality of regenerator disks is between about ¼ inch and one foot.
 4. The regenerator of claim 1, wherein a width of the gaps is between about 20 μm and about 30 μm.
 5. The regenerator of claim 1, wherein a width of the ribs is between about 30 μm and about 130 μm.
 6. The regenerator of claim 1, wherein the plurality of ribs and the plurality of gaps are concentric.
 7. The regenerator of claim 6, wherein, for each of the plurality of regenerator disks, a common center of the plurality of concentric ribs and a common center of the plurality concentric gaps are at about a center of the disk.
 8. The regenerator of claim 6, wherein, for each of the plurality of regenerator disks, the concentric ribs extend less than 360° about a common center.
 9. The regenerator of claim 8, wherein, for each of the plurality of regenerator disks, the concentric ribs extend about 120° about the common center.
 10. The regenerator of claim 8, wherein, for each of the plurality of regenerator disks, the angular positions of plurality of concentric ribs about the common center are aligned.
 11. The regenerator of claim 8, wherein, for each of the plurality of regenerator disks, the angular positions of plurality of concentric ribs about the common center are offset.
 12. The regenerator of claim 1, further comprising an outer cylinder and wherein the regenerator disks are positioned within the outer cylinder.
 13. The regenerator of claim 12, further comprising a cap positioned at a first end of the outer cylinder.
 14. The regenerator of claim 1, further comprising a shrink tube surrounding the regenerator disks.
 15. The regenerator of claim 1, wherein each of the plurality of regenerator disks comprises a ridge on a first surface and defines a corresponding groove on a second opposite surface.
 16. The regenerator of claim 15, wherein at least a portion of the ridges are thermally insulating.
 17. The regenerator of claim 15, wherein the ridge and the groove extends completely around a common center of the concentric ribs.
 18. The regenerator of claim 1, wherein at least a portion of the plurality of regenerator disks are thermally insulating.
 19. The regenerator of claim 1, wherein the at least a portion of the plurality of regenerator disks that are thermally insulating are selected from the group consisting of regenerator disks made from a thermally insulating material and regenerator disks having a thermally insulating coating.
 20. The regenerator of claim 1, wherein the plurality of ribs and the plurality of gaps are linear.
 21. The regenerator of claim 20, wherein the plurality of ribs are parallel to one another.
 22. The regenerator of claim 1, wherein each of the plurality of ribs comprises a plurality of alternating portions meeting one another at angles of less than 180°.
 23. The regenerator of claim 22, wherein the plurality of ribs are parallel to one another.
 24. A regenerative engine comprising: a regenerator, the regenerator comprising: a plurality of regenerator disks, wherein each of the plurality of regenerator disks comprises a plurality of concentric ribs defining a plurality of concentric gaps therebetween, and wherein the plurality regenerator disks are arranged within the regenerator longitudinally, such that the plurality of concentric gaps defined by adjacent regenerator disks are substantially aligned; a pulse tube comprising a cold end and a hot end, wherein the pulse tube is in fluid communication with and is coupled to the regenerator at the cold end; a reservoir, wherein the reservoir is in fluid communication with the pulse tube at the hot end of the pulse tube; a working fluid positioned within the regenerator, the pulse tube, and the reservoir; and a phase control device positioned in a fluid path between the hot end of the pulse tube and the reservoir.
 25. The regenerative engine of claim 24, wherein the pulse tube and the regenerator share a common outer cylinder, and where the plurality of regenerator disks are positioned within the common outer cylinder.
 26. The regenerative engine of claim 24, wherein each of the plurality of regenerator disks comprises a ridge on a first surface and defines a corresponding groove on a second opposite surface.
 27. The regenerative engine of claim 24, wherein, for each of the plurality of regenerator disks, the concentric ribs extend less than 360° about a common center.
 28. A regenerator for use with a regenerative engine, the regenerator comprising: a plurality of regenerator disks; wherein each of the plurality of regenerator disks comprises a plurality of concentric ribs defining a plurality of concentric gaps therebetween; wherein the plurality regenerator disks are arranged within the regenerator longitudinally, such that the plurality of concentric gaps defined by adjacent regenerator disks are substantially aligned; wherein a diameter of the plurality of regenerator disks is between about ½ inch and one foot; wherein a width of the concentric gaps is between about 20 μm and about 30 μm; wherein a width of the concentric ribs is between about 30 μm and about 130 μm; wherein, for each of the plurality of regenerator disks, a common center of the plurality of concentric ribs and a common center of the plurality concentric gaps are at about a center of the disk; wherein, for each of the plurality of regenerator disks, the concentric ribs extend less than 360° about a common center; and wherein each of the plurality of regenerator disks comprises a ridge on a first surface and defines a corresponding groove on a second opposite surface. 